A Tunisian-born man who "previously resided" in Canada has been arrested in the U.S. and is being linked to a man recently arrested in Canada in connection with an alleged plot to derail a passenger train.

Ahmed Abassi is accused by American investigators of fraudulently applying for a visa to stay in the United States to "facilitate an act of international terrorism." More charges may also be sought, officials have told a U.S. judge.

"As alleged, Ahmed Abassi had an evil purpose for seeking to remain in the United States — to commit acts of terror and develop a network of terrorists here, and to use this country as a base to support the efforts of terrorists internationally," U.S. Attorney Preet Bharara said in a statement.

U.S investigators say that while they were monitoring him, Abassi met with Chiheb Esseghaier, a 30-year-old Tunisian living in Montreal who was recently arrested in Canada in connection with the alleged rail plot.

Chiheb Esseghaier, one of two men detained in Canada accused of plotting a terror attack on a rail target, had been 'previously radicalized' by Ahmed Abassi, U.S. officials say. (Chris Young/Canadian Press)

Abassi was arrested in New York City on April 22 at John F. Kennedy International Airport, the same day Canadian officials announced the arrest of Esseghaier and Toronto-area resident Raed Jaser, 35. Canadian authorities allege the two men arrested in Canada were planning to carry out an attack against a Via passenger train travelling between the U.S. and Canada.

Abassi, 26, denied the immigration fraud charges during a secret arraignment a week ago, telling the judge, "Your honour, I am not guilty." His lawyer Sabrina Shroff declined to comment.

In a court appearance Thursday, Abassi told U.S. District Judge Miriam Goldman Cedarbaum that he understood that he will be spending the time before his next court appearance on June 11 preparing his case with his lawyers.

Abassi monitored by undercover agent in U.S.

U.S. officials said Abassi came to the U.S. in mid-March. While he was in the U.S., he was under surveillance "at all times," law enforcement officials said in the statement. He was also in contact with a man who was an undercover FBI agent.

While in New York City, Abassi met with Esseghaier, officials said in the statement, noting that the man recently arrested in Canada was "previously radicalized by Abassi."

During discussions with Esseghaier and the undercover agent, the statement says Abassi "discussed his desire to engage in terrorist acts against targets in the United States and other countries, and his intention to provide support and funding to organizations engaged in terrorist activity."

Many of these conversations were recorded by the undercover agent, the statement says.

Esseghaier 'dismissive' of bacteria plot

Abassi also spoke of his desire to recruit others for terrorist plots, the statement alleges.

Further details about Abassi were revealed in a letter filed by U.S. prosecutors with a New York court. In the letter, U.S. prosecutors say Abassi, Esseghaier and the undercover agent also discussed Esseghaier's "proposed terrorist plots."

The letter says that Abassi told the undercover agent that Esseghaier's plans "were good" but the time wasn't right.

"The defendant noted that he had suggested an alternative plot contaminating the air or water with bacteria in order to kill up to 100,000 people — but that Esseghaier was dismissive of that plan," the letter says. The letter notes that no steps were taken to further a contamination plot that would have endangered the public.

The letter also says that in an interview with law enforcement officers, Abassi acknowledged that he "may have radicalized" Esseghaier, and said he and Esseghaier "discussed plots to poison a water system and to derail a passenger train."

The indictment charges Abassi with two counts of knowingly making false statements to immigration authorities to facilitate an act of international terrorism. If convicted, each count could bring a sentence of up to 25 years in prison.

In the letter to the court, U.S. prosecutors noted that they are considering filing more charges but didn't specify what they might be.

The U.S. Attorney's Office said Abassi's next court date is scheduled for June 11 in New York City.

"While I cannot comment on operational matters related to national security, I would like to congratulate the FBI for this significant arrest," Public Safety Minister Vic Toews said in a statement.

In Canada, Jaser and Esseghaier are charged with conspiracy to carry out a terrorist attack and conspiring to murder people at the direction of, or in association with, a terrorist group in relation to the alleged train plot.

They denied the charges against them at separate court appearances and were remanded to custody pending their next court appearance later this month.